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History of EARTH

The earth is third nearest planet from the Sun in Solar system. As per evidence the earth was formed about 4.5 billion years before and it is the only planet where lives exist. The earth rotates around the sun and to complete one revolution takes 365.256 days which is known as sidereal year. During this rotation the earth also rotates on its own axis and it may be 366.256 times. We calculate one year for 365 days and to maintain yearly calendar consistency we add one day in every four years which is called leap year.

The earth is tilted by 23.4 degree on its axis with respect to rotation around the sun which causes the formation of seasons on the earth.

Formation of the Earth :

As we know that earth was formed about 4.5 billions years before by accretion by solar nebula. In early stage giant impact collision of earth with huge body causes the formation of moon. As the time passes, earth was going to cool and outer crust is formed and liquid water is formed. The volcanic activities and outgases created oceans and atmosphere but at early stage there was no oxygen.

What is structure of Earth ?

Earth belongs to four main layers. Outer most crust, mantle, outer core and in center inner core.

The inner core is made of Nickel and Iron having temperature 5400 degree Celsius with 1221 kms. Inner core is covered by outer core having thickness 2300 kms mainly of Iron and Nickel fluids. The outer core is covered by 2900kms thick layer called mantle which is made of hot viscous mixture of molten rocks. Outer most layer is crust about 30mm thick.

The crust is 1% of total earth’s volume. About 71% of earth surface area is covered with water in the form of oceans. Remaining 29% is solid land which includes land, lakes, rivers and island. Two poles are covered with thick ice plates. Earth’s center is liquid iron core called magma.

There are two types of crust. One is continental crust which is thicker about 30 to 50km made of more felsic, less dense rock like granite. Other is oceanic crust which is 5 to 10km thick made of more mafic, denser rocks like basalt.

Now, the earth has giant tectonic plates and ocean crust but, In early stage of the earth, this tectonic plates are too smaller. As the time goes earth becomes cool and lava convert into rocks and liquid water starts condensed and forming of ocean was started. These all platens are floating over mantle and moving to release heat of center of earth.

As the deep increases in crust, temperature increases and reaches from 200 C to 400 C due to geothermal energy. Outer side of crust is cold than inner side because it is exposed to atmosphere.

What are layers of Atmosphere?

According to evidence, the earth is the only planet in universe which belongs blanket of atmosphere surrounding it. This layer contains mixture of gases which sustain by gravity and allow the life to survive. The atmosphere protects the earth by heatwaves and ultraviolet rays coming from the sun and also keep the earth warm being cool by greenhouse effect.

Structure of air:

Nitrogen : 78 %

Oxygen : 21%

Argon  : 0.93%

Carbon Dioxide : 0.04%

Other gases like hydrogen, helium, neon, methane, water vapor etc…

The atmosphere of the Earth consists 5 layers.


It is the first layer from earth’s surface which is upto 12km from sea level. But it is varies from 9 km at poles to 17 km at equator in height. As  height increases temperature is decreases in this layer. About 80% of mass of atmosphere is present in this layer. All weather done in troposphere and suitable for life. About 99 % water vapor present in the layer. At the top of the layer there is boundary is called tropopause in which temperature becomes steady about -15 C.


It is the second layer after troposphere which starts from 12 km to 50km. In this layer, air is dry, thin and hot with no turbulence and temperature is increases as grow up. Ozone (O3) layer is present in this stage which prevents harmful UV rays coming from sun. Heavy commercial jets flow in lower stratosphere layer due to zero weather producing air turbulence.


It is the third layer starts from stratosphere and end at below thermosphere from 50km to 90 km from sea level. Temperature is gradually decreases and at mesopause temperature is -85 degree C. It is very cold portion of atmosphere. The air is too thin in this layer and air pressure at bottom of layer is 1% of sea level.


It is the forth layer of atmosphere starts from 90km of sea level and extend up to 500 km to 1000km. Thermosphere is very hot in day and very cold in night. Generally satellites  and aircrafts moving around earth in this phase. Temperature of this layer is gradually increasing according to height. This layer is totally free from water vapor and clouds

The Aurora Earth’s southern and northern lights are present in thermosphere. Charged particles in this layer collide with molecules and atom which give higher energy to particles which generate lights which shown as Aurora at poles.


It is the outer most layer of earth’s atmosphere. It is starts from 700km from sea level to 10000kms where it migrates into magnetosphere. Very close to exobase, very low density of molecules of hydrogen, helium and other gases are present.

Evolution of life

It is challenge for scientists to say when life on the earth was begin but according to evidence found the life on the earth was starts about 3.8 billion years ago. The first life forms are microfossils of bacteria developed in ocean.

Water and carbon are the main sources for the life on the earth. Carbon is easily available from atmosphere in the form of carbon dioxide and provide stable framework for life. Three possibilities for how did life create from nonliving chemicals. Self Replication means producingoffspring which are similar to itself. Metabolism means feed and repair. External cell membrane means it allow the food to enter and leave waste product.

Have a nice day !!!

ShakeTheMind View All

Authored by BK Suthar.
This site is about various topics of astronomical and geographical things which present in universe and also surrounding us. It will give you information about various planets, incidents occurs in universe and also about nature.

Have a good day !!

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